Process for the reduction of nitronaphthenes



y r. F. DOUMANI ETAL 2,4233% PROCESS FOR THE REDUCTION OF NITRONAPHTHENES Filed Hgrch 14, 1944 7170MM$ .DouMA/m C L AREA/C E. 5. Cos,

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Patented July 1, 194"? PROCESS FOR THE REDUCTION OF NITRONAPHTHENES Thomas F. Doumani, Los Angeles, and Clarence S. Coe, Long Beach, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application March 14, 1944, Serial No. 526,421

13 Claims.

This invention relates to the preparation of derivatives of naphthene hydrocarbons and applies particularly to preparation of oxygenated derivatives such as cyclohexanone oxime and cyclohexanone by a process involving initial nitration of the naphthene, followed by reduction oi the nitro-compound to the oxime, and hydrolysis of the oxime to the ketone. This is a continuation in part of copending application S. N. 512,796.

The chemistry of the naphthene hydrocarbons is not well known, since they are not as reactive as the olefinic and aromatic hydrocarbons, and are not as readily available in pure form as are the paraflins. For these reasons, the more valuable derivatives of the naphthene hydrocarbons have usually been prepared in the past by making the corresponding aromatic hydrocarbon derivative, and hydrogenating it. With the advent of improved methods of separation of naphthenes from paraffins in petroleum fractions, however, pure naphthenes are becoming more readily available, and it is the object of this invention to provide a method for producing valuable naphthene derivatives directly from the parent naphthene.

It has been found that th naphthenes, particularly cyclohexane, may be treated with nitric acid to obtain excellent yields of the mono-nitro substitution product (nitro-cyclohexane) and a single oxidation product, adipic acid.

It has now been 'discoveredthat further valuable derivatives, may be obtained from the naphthenes. Particularly it has been found that the nitrocyclohexane prepared as above or in any other suitable manner, may be further treated by th reduction and hydrolysis processes described below to obtain cyclohexanone oxime, cyclohexanqne, cyclohexanol, cyclohexylamine and other valuable derivatives, with hydroxylamine as a byproduct. The reactions may be diagrammed as follows:

Nitrocyclohexane (Reduction) w 7 H 1 f 011 011 l Possible intermediate (acid :NOH hydrolysis) -O --v NHIOH Hydroxylamine Cyclphexanone Cyclohexanone OXlmB 1 (Reduction)' (Reduction):

H 5 -NHOH 0H (acid NH 0H hydrolysis) Hydroxylamine N-Cyclohexyl Cyclohexanol l0 hydroxylamine (II) 1 (Reduction) H H NH N Cyclohexylamine Dicyclohexylamine (III) 1 Compounds I and II above may be considered as intermediates which may be termed in the reduction of nitrocyclohexane to cyclohexyl-' amine; In the ordinary methods of carrying out this reduction, there is no apparent formation of these compounds. In the reduction process of this invention, however, nitrocyciohexane is treated catalytically with hydrogen and simultaneously extracted with water to remove the cyclohexanone oxime (I) and the substituted hydroxylamine (II) as formed, indicating that the above is the mechanism for th reaction. Since I and II may be hydrolyzed as indicated, to obtain cyclohexanone,cyclohexanol, and hydroxylamine, all of which are of considerable value, the process appears to have commercial importance.

The reduction process of this invention may be carried out as indicated in the attached drawing. Referring to the drawing, th nitrocyclohexane or other nitronaphthene is introduced through line I into the upper part of tower 2 which is packed with a hydrogenation catalyst and operatedhot and under pressure as described below. Water is introduced into the lower part of tower 2 through line 3, together with hydrogen from recycle line 4 and make-up line 5. The water and hydrogen pass up through the catalyst bed in tower 2 while in intimate contact with the down-flowing nitronaphthene, the latter preferably being the continuous phase. A portion of the nitronaphthene is reduced by contact with the hydrogen and the catalyst, and reduction products I and II above which are more soluble in water than are nitrocyclohexane or III, are

immediately extracted by the water. The excess hydrogen and the aqueous extract are separated from the nitronaphthene in the top section of tower 2 and flow out the top through line 6, and are separated from each other in vessel 1 while still hot, the hydrogen being recycled to tower 2 through lines 8, l and 3 and the aqueous solution being drawn of! through line 9. The latter solution is then cooled in cooler l and discharged into vessel l I, in which the cyclohexanone oxime crystallizes out and is separated by settling, filtration, or centrifuging, and is drawn of! via line 12. Some of the mother liquor is withdrawn via line 13 and treated for further recovery of watersoluble products if desired and the remainder is recirculated via line l4 and 3 to reactor 2. The bottoms from reactor 2, consisting largely of unchanged nitrocyclohexane, with some of the less water-soluble products such as cyclohexylamine, are withdrawn via line 15, and recirculated to the nitrocyclohexane feed line 1 via line 16. A portion of this recycle material is withdrawn through line H, and purified of volatile reaction products such as the amine by distillation in column 18, the overhead being withdrawn through line l9, and the bottoms being returned to line is via line 23. In this distillation, steam, admitted through line 2 I, may be used advantageously.

Pumps, valves, etc., are not shown in the drawing, but are to be inserted where required, as would be apparent to one skilled in the art. It is also apparent that vessel ,1 may be a mere extension of the upper partof tower 2, operating at reactor pressure, or may operate at a lower pressure.

As catalysts for use in tower 2 in the above process, we may employ metals or compounds of metals of the first, second and third "transitional" groups, and particularly the metals of group VIII, preferably supported on a granular carrier to provide a large exposure of surface area. In the transitional groups it is meant to include those metals whose differentiating electron is in the second from the outermost shell. The first transitional group includes the elements having atomic numbers 21 to 30, i. e., scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc. .The second transitional group includes the elements having atomic numbers between 39 and 48, i. e., yttrium, zirconium, columbium, molybdenum, masurium,

ruthenium, rhodium, palladium, silver and cadmium. The third transitional group includes the elements having atomic numbers 5'7 and '12 to 80 inclusive, 1. e., lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold and mercury. These include the group VIII metals iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium,'iridium and platinum, of which nickel and platinum are preferred. The catalysts are preferably prepared by adsorbing on a granular carrier such as asbestos, carbon, clay, alumina, silica gel or the like, a solution of a soluble salt of the desired metal or metals, drying the impregnated solid and decomposing and reducing the salt to the free metal.

In tower 2 the temperature should be high, between about 100 and 350 C., with superatmospheric pressures sufllciently high to keep the water and nitronaphthene in the liquid state. Pressures up to about 100 atmospheres may be employed. The hydrogen should be present in substantial molal excess over the nitronaphthene, and may be-diluted with inert gases such as nitrogen if desired. Flow rates should be controlled to give contact times between about 1 minute and 1 hour or possibly more, depending on the temperature, catalyst activity, etc. In another mode of operation the nitronaphthene is introduced into tower 2 only at a rate sufllcient to replace that which is reacted and removed by the water, thus allowing the water and hydrogen to bubble up through a. relatively static nitronaphthene phase which is in contact with the catalyst. In another mode of operation the nitronaphthene may be introduced near the bottom of tower 2, together with the hydrogen or aqueous phase if desired, and allowed to separate from the aqueous phase and the hydrogen phase at the top of the tower above the catalyst bed, withdrawing the three phases separately and recirculating as desired.

As specific example of the above operation, nitrocyclohexane may be introduced into line Iv at a rate of about 375 volumes per volume of catalyst per hour, with a recycle flow through line l6 of about 3'75 volumes per volume of catalyst per hour. Water (including both recycle water from line H and make-up water from line 3) may be introduced to tower 2 at a rate of about 750 volumes per volume of catalyst per hour, and enough hydrogen used to keep the pressure at 1000 lb. gage and to keep a reservoir of hydrogen in the top of vessel 1, with a reasonable flow up through tower 2. The contact time, estimated on the assumption of 50% voids in the catalyst, with 50% of the void space occupied by hydrogen gas, and 50% of the liquid being water, is about 1 minute for the above flow rates. The temperature in tower 2 may be about 150 C. The flow through the purification system, lines l1 and 20, and tower I8, need only be about 25 volumes (per volume catalyst) per hour, with an amine production of only about 4 volumes per hour, or 1% of the feed. The aqueous extract withdrawn from vessel! will be saturated with oxime (I) and contain small amounts of compound II. When depressured and cooled to about 80 F., the crystallized oxime may be recovered at a rate corresponding to a conversion of about 10%. If desired, the streams in lines 14 and 20 may be further purified by distillation of the nitrocyclohexane or removal of other reaction products before recirculation.

The catalyst employed in the above specific example was prepared by adsorbing an aqueous nickel nitrate solution on activated carbon and drying, igniting and reducing the product to obtain a catalyst containing about 5% metallic nickel. Employing the same catalyst in the conventional process of reduction, 1. e., by subjecting nitrocyclohexane to a temperature of 150 C. in contact with the same catalyst and hydrogen at a pressure of 5001b. gage, cyciohexylamine may be obtained, but no trace of the oxime (I) or compound II.

The cyclohexanone 'oxime (I) may be hydrolyzed to form cyclohexanone and hydroxylamine I according to the equation shown above. The hydrolysis may be carried out by contacting the oxime with dilute aqueous mineral acids (hydrochloric, sulfuric, nitric, etc. of 0.1 N'to 10 N concentration) at temperatures between about 0 C. and 150 C. For example, by adding 1 gram mol of the oxime (I) to 200 ml. of 5 N sulfuric acid, and heating at about C. for 10 minutes, the oxime is converted quantitatively to the ketone and hydroxylamine sulfate. By merely chilling,

the bulk of the ketone may be separated as an I oily layer, and the hydroxylamine sulfate ma be crystallized out. Better separation may be of the water. By chilling the overhead and bot-' toms, the ketone and salt are recovered separately from the two fractions, as oil and crystalline solid,

respectively.

The cyclohexanone formed as above may be reduced to cyclohexanol by known methods, or converted to other valuable derivatives. Cyclohexanol may also be prepared directly by hydrolysis of compound II separated from recycle stream [4, the hydrolysis being carried out under substantially the same conditions given above for hydrolysis of the oxime.

Although specific conditions of operation have been shown above, the invention is not to be limited thereby, for the process may be carried out under other conditions in the ranges indicated. Various comblnationsof the above processes may be used. For example, if a dilute mineral acid as described above is used instead of water, in line 3 and tower 2, the oxime (I) and compound II may be hydrolyzed as formed, and the extract withdrawn from vessel 1 through line 9 may contain littleor no I or II, but instead, contain the hydrolysis products cyclohexanone, cyclohexanoi, the hydroxylamine salt, and also the cyclohexylamine salt. This complicates the recovery problem somewhat, but suitable modifications of the methods described may be employed, as will be apparent to one skilled in the art.

The above description of the processes of this invention has been confined largely to the treatment of cyclohexane. It is to be understood, however, that other naphthenes will respond to similar treatments and yield analogous products. Qther unsubstituted naphthenes such as cyclopentane and cycloheptane, will respond in substantially the same way as cyclohexane. When substituted naphthenes are employed, larger numbers of derivatives are obtained. For example, with methyl cyclohexane, the following types of nitronaphthenes may be formed:

H H CH: 0101mm, QZNO, 0 1m, Hm CE:

Primary Secondary Tertiary It is apparent that where other substituted naphthenes such as dimethyl cyclopentane, ethyl cyclohexane, ispropyl cycloheptane, and the like, are employed, products corresponding to those shown above may be obtained.

It has been,,found that in the above oxidation process, small amounts of dinitrodicyclohexane are formed. This may be reduced by the novel hydrogenation process described above to obtain bicyclic derivatives corresponding to those made Dlnitrodicyclohexanc (Reduction) NO ON a i I NHOH on O Y I +NHIOH NH, N H:

' The above compounds (except the hydroxylamine and the dinitrodicyclohexane) are all new compositions of matter, as are the corresponding derivatives prepared from the other unsubstituted and the substituted naphthenes as described above.

Modifications of the above processes which would reasonably occur to one skilled in the art are to be included in the scope of this invention as defined in the following claims.

We claim:

1. A process for the reduction of nitronaphthenes which comprises passing two streams, one of which is a gaseous stream comprising hydrogen and the other is water, through a body of liquid.

nitronaphthene which is at a temperature above about 100 C., at a pressure sufficient to maintain the water and the nitronaphthene in the liquid state and which is in contact with a hydrogenation catalyst, whereby the nitronaphthene is reduced to the corresponding oxime, and hydrolyzing said oxime with a dilute aqueous solution of a mineral acid to form the corresponding ketone.

2. A process according to claim 1 in which the reduction and hydrolysis are effected simultaneously by employing a dilute aqueous solution of mineral acid'in place of water.

3. A process according to claim 1 in which the reduction and hydrolysis are effected simultaneously by employing a dilute aqueous solution of mineral acid in place of water and the ketone is extracted into the aqueous phase, removed irom the reaction zone as formed and recovered from the aqueous phase.

4. A process according to claim 1 in which the reduction and hydrolysis are efiected simultaneously by employing a dilute aqueous solution. Of mineral acid in place of water and in which the nitronaphthene is nitrocyclohexane and the ketone is cyclohexanone.

5. A process according to claim 1 in which the nitronaphthene is a secondary nitronaphthene.

6. A process according to claim 1 in which the nitronaphthene is nitrocyclohexane and the ketone is cyclohexanone.

7. A process according to claim 1 in which the hydrogenationcatalyst comprises a metal selected from the first, second and third transitional groups. I

8. A process for the reduction of nitronaphthenes which comprises passing two streams, one of which is a gaseous stream comprising hydrogen and the other is water, through a body or liquid nitronaphthene which is at a temperature above about 100 C. and at a pressure sufficient to maintain the water and the nitronaphthene in the liquid state and which is in contact with a hydrogenation catalyst, whereby the nitronaphthene is reduced to the corresponding oxime.

9. A process for the reduction of nitronaphthenes which comprises passing two streams, one of which is a gaseous stream comprising hydroge and the other is water, through a body of liquid nitronaphthene which is at a temperature above about 100 C. and at a pressure suflicient to maintain the water and the nitronaphthene in the liquid state and which is in contact with a hydrogenatio catalyst, whereby the nitronaphthene is reduced to the corresponding oxime and said oxime is extracted into the aqueous phase, removed from the reaction zone as formed and recovered from the aqueous phase.

10. A process according to claim 9 in which the nitronaphthene is a secondary nitronaphthene.

11. A process according to claim 9 in which the nitronaphthene is nitrocyclohexane and the oxime is cyclohexanone oxime.

12. A process according to claim 9 in which the hydrogenation catalyst comprises a metal selected from the first, second and third'transitional groups.

13. A process according to claim 9 in which the temperature of the nitronaphthene is maintained between about C. and 350 C.

THOMAS F. DOUMANI. CLARENCE S. COE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

